Question
What is meant by “direct sampling” in software defined radios?
Answer Options
- A) Software is converted from source code to object code during operation of the receiver
- B) I and Q signals are generated by digital processing without the use of RF amplification
- C) Incoming RF is digitized by an analog-to-digital converter without being mixed with a local oscillator signal
- D) A switching mixer is used to generate I and Q signals directly from the RF input
Correct Answer: C
Explanation
Direct sampling is one of the most advanced architectures used in Software Defined Radios (\text{SDRs}). It bypasses the traditional superheterodyne process (amplification, mixing, IF filtering) to convert the radio signals into digital data as early as possible in the signal chain.
In a direct sampling \text{SDR}, incoming \text{RF} is digitized by an analog-to-digital converter (\text{ADC}) without being mixed with a local oscillator signal. The high-speed \text{ADC} samples the entire \text{RF} spectrum of interest (e.g., the whole \text{HF} band) directly, and all subsequent processes, including filtering, mixing, and demodulation, are performed in the digital domain by a powerful processor.
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